Minnesota teen Zach Sobiech, who wrote the viral hit "Clouds" during his bone-cancer fight, died Monday morning. He was 18.

"With heavy hearts" the Children's Cancer Research Fund announced the news on its website, writing, "Zach was at home and at peace with those he loved most. Zach's life ended just as he lived, embraced by the love of his family, friends, grace and music."

Sobiech, who celebrated his 18th birthday on May 3, was diagnosed with osteosarcoma when he was 14, and was told by doctors last June that he had possibly less than a year to live. That December, he released "Clouds." The song about facing death got more than three million YouTube views. Just this month, Rainn Wilson led a group of celebrities lip-syncing in a moving tribute video.

Now, a slew of celebrities are showing their support for the brave teenager (he's been diagnosed with osteosarcoma) with a tribute video set to his song, in an effort to raise awareness and funds to help find a cure for childhood cancer.

Jason Mraz fans anticipating his upcoming nuptials to singer Tristan Prettyman may have a long road ahead of them. The musical couple say they plan to wait to wed until same-sex marriages are legal.

"Before I got engaged, I said that I don't want to get married until marriage is equal for all," Mraz, 33, told PEOPLE at last week's Elton John benefit concert for the American Foundation for Equal Rights in Beverly Hills. "So now I'm engaged, and we want to get married some day. So this kind of really puts us in the fight."

Mraz, who popped the question in December, is hopeful and even confident that he'll be able to say "I do" before too long.